Measuring device and method for reducing measuring errors

ABSTRACT

The invention relates to a device for determining the non precise placement of measuring sites on measuring sensors and for reducing measuring errors, which result from the movement between the measuring sites and the measuring sensors when measuring the most diverse quantities to be measured, with the aim of creating robust measuring systems for recording measured values under real or challenging conditions. The invention is characterized by: detecting whether and which sensor elements are covered and thus in contact with the site to be measured; tracking and/or adapting the sensor elements so that the contact is not interrupted even during movements, and; the resilient arrangement of the contacts for constantly maintaining the mechanical bearing pressure when measuring the electrical skin resistance. The measurement data are processed further by software that determines the area of contact from the signals from the device and from the knowledge of the arrangement of the measuring elements, and uses the completely covered sensor elements determined thereby in order to conduct measurements with the fewest possible number of errors.

CROSS REFERENCE OF RELATED APPLICATIONS

This application claims the benefit of Austrian Patent Number 410844,mt. Cl. G01D 3/028, entitled “Messvorrichtung Und Methode Zur ErmittlungVon Ungenauem Anlegen Von Sensoren Und Reduzierung Von Messfehlern FürRobuste Messsysteme Für Z.B. Physiologishe Messgrössen,” filed inAustria on Mar. 25, 2002, by Christian Stockinger and PCT ApplicationNo. PCT/AT03/00073, entitled “Measuring Device And Method For ReducingMeasuring Errors”, filed Mar. 13, 2003, by Christian Stockinger, theentire contents of both applications are hereby specificallyincorporated by reference herein for all they disclose and teach.

1:1. INTRODUCTION

The present invention applies to acquiring measuring values asaccurately as possible from a testing site of interest.

Physiological values from the human or animal body (e.g. skinresistance, temperature, circulation, etc.) may be given as examples.The sensors for these values can be mounted on items like a steeringdevice or control device, a data input device, a mobile data processingunit or a mobile telephone, which the user uses while the measurement istaken.

This has diverse applications, such as monitoring certain conditions,stress monitoring, relaxation training, fitness training, games,performance improvement, diagnostics and training of bodily functions toheal and alleviate discomfort and sicknesses, work ergonomicapplications etc.

Skin resistance and temperature are the values exemplarily used toillustrate the descriptions.

As a matter of principle, other values such as circulation, oxygensaturation, surface hardness, electrical activity, heat dissipation etc.as well as values from other surfaces than the human or animal bodysurfaces can be measured with this invention, with a reduction ofmeasuring errors.

The resulting measured values and the auxiliary values are measured andfurther processed in data processing devices.

1.2. STATE OF THE ART

1.2.1. Anticipations

As shown in patent JP11118636A (Tokai Rika Denki KK), Apr. 30^(th) 1999a multitude of sensor elements is used in one sensor device, the sensorelements of which are used together. Here sensors of the same type areused which are correlated with each other and whose signals areprocessed concertedly. From this output values are calculated, whichotherwise could not be obtained from one sensor alone. The inventiondescribes a method, to produce a well-protected and miniaturized sensorarray.

The patent JP9215667A (Nippon Koden Corp.), Aug. 19^(th) 1997 describesa multitude of sensors in a measuring device, which together deliver asummary result. For the described EKG-sensor, three kinds of sensorswork together (inverting contact, not inverting contact and referencecontact of an instrumentation amplifier), to measure a value from theskin as accurately as possible. The joint structure in one device allowseasy manageability and reduces measuring errors. The spring-mountedarrangement of the contacts allows an adaptation to the skin surface.

The novelty of the present invention when compared to the twoanticipations is, that two kinds of sensors or two kinds of data, whichcan be derived from sensors, are used in a shared sensor element. Indoing so one sensor's information and the known geometrical position ofthe sensors relative to each other are used to evaluate the correctnessof the other sensor's information (if and which sensor elements havecontact, if and which sensor elements are completely covered).

To further reduce measurement errors, the sensor elements are alsomovable and/or pliable and therefore can follow the test site duringmovements. Additionally, for the measurement of the skin resistance toobtain an as advantageously steady as possible bearing pressure, thecontact areas or the complete sensor are spring-mounted.

1.2.2. Other Publications

The measurement of physiological values under difficult circumstances isdescribed in DE 199 59 576 A1. It does not, however, include the specialcontact, coverage and complete coverage, and prevention of interruptedcontact assuring mechanisms and, in the case of the skin resistance, thesteady bearing pressure in the framework of such a device.

In the example of a physiological measurement on the skin in EP1 109 382A2, assuring mechanisms are described that ensure contact through twodifferent sensor systems. However none are described for coverage andcomplete coverage, prevention of interrupted contact, and in the case ofskin resistance, the steady contact pressure in the framework of such adevice.

As shown in U.S. Pat. No. 6,067,468, the application of the sensors istaken for granted. The users usually are advised to be sure to have acorrect and steady application of sensor elements and to make as littleas possible or no movements at all during the measurement.

1.3 PROBLEM

Basically, all measurement values are measured with correspondingmeasurement sensors. Sensors do have a geometric dimension and have tobe in one way or other in contact or interaction with the testing site(corresponding to the kind of sensor element used).

While taking measurement values from a testing site which does notaccurately fit the sensor elements, and/or is moving, as in the casewith a user who uses a device with one or more mounted sensors, thefollowing main problems make a simple and reliable measurementinaccurate or even impossible:

-   1. Problem of detecting the contact of the sensor element:

To obtain useful measured values, one has to determine whether a testingsite is contacting the sensor elements at all. If the sensor hasmultiple sensor elements, it needs to be determined which of thesesensor elements are in contact with the testing site. Therefore whatneeds to be detected is, whether and which sensor elements are incontact with the testing site.

-   2. Problem of the complete coverage of sensors:

Sensor elements have a geometric dimension, a size. This implies, thatunder some circumstances, especially when the testing site is notperfectly fitting the sensors or during movements, sensors will not becompletely covered or not completely covered at all times by the testingsite, although a contact of the testing site with the sensor elements assuch is given. This leads to large measuring errors.

Further problems, preventing a simple and reliable measurement or makingit impossible:

-   3. Problem of loosing contact during movements:

If sensor elements are completely covered and if a movement between themand the testing site occurs during the measurement, be it a movement ofthe sensor or be it a movement of the testing site, measuring errors canhappen due to lost contact. This is the case when sensor elements arestationary on a testing site as well as when they are moved on a testingsite.

-   4. Problem of the contact bearing pressure for skin resistance:

In the case of the physiological measuring value skin resistance,changes of the value of the skin resistance measurement signal are alsopossible through a change of the bearing pressure of the sensors on theskin. This happens for example through having more or less pressure ofthe skin onto the sensors. This leads to measuring errors in the skinresistance measurement.

The invention solves the problems described above.

INVENTION TO SOLVE THE PROBLEMS DESCRIBED ABOVE

1.4.1. Solving the problems of detecting sensor element contact and thecomplete coverage of the sensor elements

1.4.1.1. By means of main sensor elements and auxiliary sensor elements

The invention is comprised of the following: The mounted sensor elementsare divided into main sensor elements and auxiliary sensor elements.There are a number of main and auxiliary sensor elements on the sensorsurface, which touches the testing site. The geometrical position of themain and the auxiliary sensor elements in relation to each other isknown to the measuring system. If necessary, one or more commonreference sensors can be used.

Once it has detected which auxiliary sensors the testing site touches,the measuring system can deduce the contact area. All main sensors thatlie in that ascertained contact area are completely covered and theirsignals are used for the actual measurement. For this, and this is veryfavorable, the auxiliary sensor elements do not need complete coverage.This means they only need to give rough values, such as being in contactor not being in contact.

Differentiation between the signals of the main sensor elements and thesignals of the auxiliary sensor elements for the data processing systemhas to be ensured. This can be solved for example by using directcurrent for the auxiliary sensors and alternating current for the mainsensors. Although the electrical signals superimpose each other on thetesting site they can be distinguished into signals from the auxiliarysensors and signals from the main sensors and thereby the contact areacan be determined.

Alternatively, the measurements that detect the contact of the sensorelements and those accomplishing the main measurement can be done withthe same measurement value and also with the same sensor elements but inconsecutive measurements. In that case it is assumed that during themain measurements (between the detection measurements) the contact ofthe sensors with the testing site does not change.

1.4.1.1.1. Example: Thumb Sensor for a computer mouse

A thumb sensor for a computer mouse is given as an example. See FIG. 1“schematic view of the detection of the complete coverage for the thumbsensor of a computer mouse”.

To ensure that all the main sensor elements, (1) and (2) for the skinresistance and (3) for the temperature, are firstly covered and secondlycovered completely, and are therefore able to fulfill their function asaccurately as possible, this sensor is comprised as follows: Severalauxiliary sensor elements are arranged geometrically around the mainsensor elements, e.g. three (7) (8) (9). The auxiliary sensors definethe contact area (5), within which the main sensor elements are located.Once it has been detected that all the auxiliary sensors are contacted,the main sensor elements (1) (2) (3), which are arranged geometricallywithin the contact area, are ensured to be covered and coveredcompletely by the contacting skin surface. For this effect, theauxiliary sensors need not to be completely covered. They only need todeliver rough measurement values, like contact or no contact.

The areas created by the auxiliary sensors and the main sensor elementsneed not be completely overlapping. It needs only to be ensured throughthe design, that by covering the auxiliary sensors, the contact area forthe main sensors is so large that the main sensors are lying within itand therefore are completely covered. For example, at the thumb creatinga triangular area by the auxiliary sensors necessarily ensures that themain sensor elements, which extend somewhat beyond that triangular area,are correctly covered. This is because the pattern of a thumb on asensor, which is mounted at the side of a computer mouse, is oval. Ifall 3 auxiliary sensors are covered, one can deduce that the mainsensors, which extend somewhat beyond the triangular area, are alsocompletely covered.

The differentiation between the signals of the main sensor elements andthe signals of the auxiliary sensor elements needs to be ensured, seeFIG. 2 “example of a signal flow from auxiliary sensor elements and mainsensor elements for a thumb sensor of a computer mouse”. In the case ofthis example for the measurement of the skin resistance at the thumbsensor (13) according to FIG. 1 this could be realized by utilizing adetection with alternating current (10) for the auxiliary sensorelements (7), (8), (9) and a detection with direct current (11) for themain sensor elements (1) (2). These signals are relatively easy todistinguish from each other. Auxiliary sensor elements and main sensorelements both have a measurement module whose output signals aredelivered for analysis to the data processing system (12). This analysisincludes the coverage detection and the measurement with completelycovered main sensors.

Alternatively the measurements with the auxiliary sensors to detect thecontact of the sensor elements and those accomplishing the mainmeasurement can be done with the same measurement value in consecutivemeasurements. Thereby it is assumed that during the main measurements(between the detection measurements) the contact of the sensors with thetesting site is not changing.

1.4.1.1.2. Example Finger Sensor

As a further example a finger sensor for a physiological measuringsystem according to FIG. 3 “schematic side view and upper view of afinger sensor with common reference electrode for main and auxiliarysensors” is given to explain, that the main and auxiliary sensors canhave an electrode in common and that through the geometrical arrangementthe complete coverage for the main measurement can be grantednevertheless.

The sensor (4) with a finger stop (25) is applied to the skin of afingertip with its contact surface (5), the contact pattern of thecontact area is oblong.

When contact is detected between the auxiliary sensor element (7) andthe contact area (2) by means of a measurement, it is assured, that themain sensor element (1) is completely covered. By virtue of theknowledge of the position and the constructive size of the sensor whichthrough the resting obstacle can only be applied to a finger tip it isassured, that the sensor element (2) is completely covered, in this caseused as main sensor element as well as auxiliary sensor element, andthus a correct measurement between the sensor elements (1) and (2) canbe performed.

The differentiation between the signals of the main sensor elements andthe signals of the auxiliary sensor elements again can occur e.g.through the use of alternating current for the auxiliary sensor elementsand through direct current for the main sensor elements.

Alternatively the measurements with the auxiliary sensor to detect thecontact of the sensor elements and those accomplishing the mainmeasurement can be done with the same measurement value (e.g. directcurrent) in consecutive measurements. Thereby it is assumed that duringthe main measurements (between the detection measurements) the contactof the sensors with the testing site is not changing.

1.4.1.1.3. Example Steering Wheel

As a further example for a sensor a steering wheel with a mountedmultitude of sensor elements for the measurement of skin resistance isgiven. In FIG. 4 “schematic view of the sensors to detect the contactarea on a steering wheel” the area to touch from the steering wheel isschematically shown unrolled as rectangle. To detect which main sensorelements (15, white) are covered through the testing site skin (of thetouching hand) and thus are able to fulfill their function as accuratelyas possible, the main sensor elements are placed between the auxiliarysensor elements (16, dotted). When it is detected which auxiliarysensors are touched by the skin, this results for the measuring systemin the contact area (14). All main sensors within this contact area arecompletely covered and are used for the actual measurement. For this theauxiliary sensors do not need to be completely covered, they have togive only rough data such as contact or no contact.

The differentiation between the signals of the main sensor elements andthe signals of the auxiliary sensor elements again can occur throughe.g. the use of alternating current for the auxiliary sensor elementsand through direct current for the main sensor elements. Or themeasurements can be performed with the same measurement value (e.g.direct current) in consecutive measurements. Thereby it is assumed thatduring the main measurements (between the detection measurements) thecontact of the sensors with the testing site is not changing.

1.4.1.2. By means of correlation of the sensor elements with each other

Here the sensor elements are not divided into main sensors and auxiliarysensors. The invention comprises a multitude of sensors, which aremounted on the sensor surface, which shall be touched. The geometricposition of the sensor elements to each other is known to the measuringsystem.

To detect, which sensor elements are covered and can fulfill theirfunction as accurately as possible this measuring device comprises, thatevery sensor element is sampled in the form of a matrix to detect withan auxiliary medium like current, light or the like or an othercharacteristic like temperature if and where a contact with the testingsite takes place.

Through this procedure results the contact area of the covered sensorelements. All sensor elements within this contact area are completelycovered and are used for the actual measurement. Attention needs to beapplied to sensor elements at the fringe of the contact area, theirmeasuring values are either to be rejected or, if possible, to becorrected.

The information of the position of the contact area itself can also beused for further processing.

As an example again a steering wheel is given and referred to FIG. 5 a“schematic view of the device to detect the contact area throughmeasurements with the sensor elements to each other”. Here a small partof the area to be touched is shown unrolled from the steering wheel as arectangle, the contact area (15) touched by the skin shall be detected.The sensor elements are arranged in a matrix, e.g. 100 sensors for eachrow, in the figure the number of the sensor element is given in theinside of the respective sensor element. Now, with one sensor elementafter the other, here e.g. Nr. 216 with its geometrically surroundingelements 115, 116, 117, 215, 217, 315, 316 and 317, measurements areperformed, sampled. In the example the processing of the measured valuesresults in contact across the testing site with the elements 117, 217,316 and 317.

With this information the system can detect, that the geometricalborderline of the testing site runs through the elements 117, 216, 316and (after a measurement with element 316 and its surrounding elements)416.

The detected contact area (17, dotted colored sensor elements) in FIG. 5b “schematic view of the contact area after the coverage detection withmeasurements of the elements to each other” with completely coveredsensors is therefore detected to be to the right from the dotted sensors118, 217, 218, 317, 318, 417, 418. After the performance of allmeasurements of all sensor elements with their respective surroundingsensor elements the complete contact area can be detected. With thisinformation the actual main measurement is performed as accurately aspossible during which it is assumed that the contact area is notchanging. In addition, if necessary, the information about the positionof the contact area is processed.

As a variation the sampling for each sensor element can be performed asa measurement with one or more common reference electrodes. Any coveredsensor element can be used as reference electrode. These referenceelectrodes could even be designated during a measurement, when in afirst measurement sequence one or more covered sensor elements aredetected which are used as reference electrodes for the next measurementsequence.

1.4.2. Solution of the problem of losing contact during movementsthrough tracking or molding of the sensor elements

The sensor elements need to make good contact with the testing site, thecontact needs to be warranted (sensor stationary on one testing site ormoving on a testing site). In the case of the first contact and movementduring the measurement this is solved by the invention by trackingand/or a molding of the sensor elements.

Therefore the invention comprises tracking the sensor elements as far aspossible according to the movements to be expected in order to not losecontact with the testing site and thus to avoid measuring errors.

In addition or alternatively the invention comprises that sensorelements themselves can be formed to the form of the testing site towarrant a correct contact. Thereby the sensor elements are pliableand/or track-able and thus fit to the testing site, even duringmovements.

This can be done with and without using a fixed matrix of auxiliarysensors. Here the auxiliary sensors are designed as being not moveableand serve as counter bearing to bear the mechanical forces of thetesting site.

1.4.2.1. Example rocker for a thumb sensor of a computer mouse

In FIG. 6 “view of a moving device with sensor elements for tracking”the sensor elements (1), (2) for the skin resistance and (3) for thetemperature are built into the vertical surface of a moving device (4)(a teeter). This teeter is inserted into the PC-mouse (6) in the regionof the thumb and follows the thumb in his movements during work with thePC-mouse. Through this tracking the contact between sensor elements andskin is granted within a wide range.

Alternatively or additionally the sensor elements (1), (2), (3) can beadjusted to the surface form of the skin to grant a correct contact tothe skin, see FIG. 7 “view onto moveable sensor elements for adjustingto the testing site”. Here the sensor elements are moving and equippedwith springs (18) and adjust themselves to the skin (26), even duringmovements.

Alternatively or additionally the sensor elements (1), (2), (3)themselves can be adjusted to the surface form of the skin to assure afitting contact to the skin. Here the sensor elements themselves arepliable. With a lightpressure they take on the form of the skin site andadjust themselves to the skin even during movements. For this thematerial of the sensor elements has to be pliable.

1.4.2.2. Examples of application at joysticks, game consoles, mobiledata processing units and mobile telephones

A joystick is a computer input device operated like a control stick ofan airplane, a game console is usually used to control electronic gameswith input buttons.

According to FIG. 8 “view onto a moving, spring-mounted device withsensor elements for tracking and in the case of the skin resistance forkeeping the pressure constant”, in this example sensor elements areinserted in a moving device. This is here a teeter (22), which can bepressed inwards along a vertical guide, which is spring-mounted by thespring (20). This sensor is for example inserted into the joystick (22),the mobile data processing unit or the mobile phone in the area of theheel of the hand and follows the skin during movements as it is used.

Alternatively or additionally the sensor elements (1), (2), (3)themselves can be adjusted to the surface form of the skin to grant acorrect contact to the skin, similar as in FIG. 7 for the computermouse. Here the sensor elements are pliable and/or spring-mountedmoveable and thus adjust to the skin, even during movements.

For not so strict demands on the precision of the measurement thetracking can be omitted, the sensor elements then are integrated in anot moveable manner (e.g. in the region of the device which reaches thepalm of the hand).

1.4.3. solution of the bearing pressure problem through keeping thepressure constant for the skin resistance measurement

A factor in measuring the electric resistance of the skin is thepressure the contact areas bear onto the skin. If this pressure changesduring the measurement by a more or less firm grip of the user, changesin the data of the electrical auxiliary physical value to register theskin resistance can occur, which are not caused by a change of the skinresistance (measuring error). Therefore the invention comprisesspring-mounted contact areas for the skin resistance. Changes ofpressure of the skin site are transferred to the material surroundingthe spring-mounted contact areas. Therefore the bearing pressure of thecontact areas onto the skin depends in a wide range only on the spring,which produces a constant bearing pressure.

In FIG. 9 “spring-mounted contact areas for the skin resistancemeasurement” the spring-mounted sensor elements (1) or (2) are assembledin the sensor (4) onto which the skin (5) presses. Through the spring(23) the constant bearing pressure of the main sensors is created,hereby enabling the main sensor to measure as accurately as possible.Pressure changes are transferred only to the surrounding sensor material(4).

In the example according to FIG. 10 “spring-mounted contact areas forthe measurement in a fixed matrix of auxiliary sensors to keep thebearing pressure constant during measurement of the skin resistance”this can be performed with a fixed matrix of auxiliary sensors. Here theskin (5) is positioned through the fixed auxiliary sensors (26, narrowlydotted), onto which the changes in pressure are transferred. For themeasuring signals of the auxiliary sensors the constant bearing pressureis not so important as long as they are contacted at all. The (dotted)main sensors (27) are pressed against the skin with the springs (24).Through the positioning of the skin (5) through contacting the auxiliarysensors a constant bearing pressure results for the main sensors whichnow can measure with a constant bearing pressure as accurately aspossible.

Alternatively the invention comprises a spring-mounting of the completesensor element to keep the bearing pressure constant. If the skin sitecan only be in a defined area it is possible by tracking the completesensor element to keep the bearing pressure constant within certainlimits and thus to keep the measuring errors small.

An example would be a joystick whose spring-mounted element according toFIG. 8 reaches the skin with a somewhat constant bearing pressure aslong as the hand encloses the joystick.

STRUCTURE OF THE ANALYZING SOFTWARE

This describes the structure of software in a data processing unit,which processes the measuring data of the error reducing measuringsensors.

1.5.1. Detection of coverage with auxiliary sensor elements

The analyzing software for the measuring error reducing sensorscomprises, that the contact area can be determined through the coveragedetection according to chapter 1.4.1.1. Along with the positioning ofthe sensor elements known to the system the states “no main andauxiliary sensor element covered”, “certain main and auxiliary sensorscovered but not completely” and “certain main and auxiliary sensorelements completely covered” can be distinguished.

In the states “no main and auxiliary sensor element covered” and“certain main and auxiliary sensors covered but not completely” themeasuring data is rejected or, if possible, corrected, and thusmeasuring errors eliminated, furthermore a warning can be given to theuser and/or an action to correct the sensors can be demanded, and thegeometric position of the contact area can be processed further.

In the state “certain main and auxiliary sensor elements completelycovered” the detected covered sensor elements can be used formeasurements, which are as accurate as possible, and the geometricposition of the contact area can be processed further.

1.5.2. Coverage detection of the sensor elements to each other

The analyzing software for the sensors with measurement error reducingthrough the coverage detection to each other comprises that the contactarea can be determined through the coverage detection according tochapter 1.4.1.2. With the positioning of the sensor elements, which isknown to the system it can distinguish between the states “no sensorelements covered” and “certain sensor elements covered and thuscompletely covered”.

In the state “no sensor elements covered” the measuring data is rejectedor, if possible, corrected, and thus measuring errors eliminated,furthermore a warning can be given to the user and/or an action tocorrect the sensors can be demanded.

In the state “certain sensor elements covered and thus completelycovered” the detected covered sensor elements can be used formeasurements as accurately as possible, and the geometric position ofthe contact area can be processed further.

1. Apparatus for measuring the electrical resistance of a portion ofskin, and for detecting imprecise placement of the portion of skin ontosensors adapted for such measurements and disposed on a surface of saidapparatus, said apparatus comprising in combination: at least two mainsensors disposed on the surface and defining an area thereon, said atleast two main sensors being capable of measuring electrical resistance;at least two auxiliary sensors disposed on the surface and outside ofthe area defined by said at least two main sensors, said at least twoauxiliary sensors being capable of measuring electrical resistance; anda processor for receiving and for analyzing measured electricalresistance from said at least two main sensors and from said at leasttwo auxiliary sensors when the portion of skin is placed in contact withsaid apparatus; whereby a measured electrical resistance from said atleast two main sensors is used in the measurement of the electricalresistance of the portion of skin only if said at least two auxiliarysensors have a measured electrical resistance.
 2. The apparatus of claim1, wherein the measured electrical resistance of said at least two mainsensors is obtained using a direct current, and the measured electricalresistance of said at least two auxiliary sensors is obtained using analternating current.
 3. The apparatus of claim 1, wherein said processordifferentiates between the measured electrical resistance of said atleast two main sensors and the measured electrical resistance of said atleast two auxiliary sensors.
 4. The apparatus of claim 3, wherein saidprocessor provides a warning if said at least two auxiliary sensors donot have a measured electrical resistance.
 5. The apparatus of claim 1,wherein each of said at least two main sensors, and each of said atleast two auxiliary sensors are capable of conforming to the shape ofthe portion of skin undergoing measurement.
 6. The apparatus of claim 5,wherein each of said at least two main sensors and each of said at leasttwo auxiliary sensors are spring-mounted to the surface such that aconstant bearing pressure of the portion of skin is produced on each ofsaid at least two main sensors and on each of said at least twoauxiliary sensors.
 7. The apparatus of claim 5, wherein each of said atleast two main sensors are spring-mounted to the surface such that aconstant bearing pressure of the portion of skin is produced on each ofsaid at least two main sensors.
 8. The apparatus of claim 5, whereineach of said at least two main sensors and each of said at least twoauxiliary sensors are pivotably mounted to the surface.
 9. Apparatus formeasuring the electrical resistance of a portion of skin, and fordetecting imprecise placement of the portion of skin onto sensorsadapted for such measurements and disposed on a surface of saidapparatus, said apparatus comprising in combination: a plurality ofsensor pairs disposed on the surface, each sensor pair in said pluralityof sensor pairs being capable of measuring electrical resistance; and aprocessor for receiving and for analyzing the measured electricalresistance from each of said sensor pairs in said plurality of sensorpairs, when the portion of skin is placed in contact with saidapparatus; whereby measurements of the electrical resistance from sensorpairs which are in partial contact with the portion of skin are used todefine a contact area, and the measurement of the electrical resistanceby sensor pairs within the contact area are used in the measurement ofthe electrical resistance of the portion of skin.
 10. The apparatus ofclaim 9, wherein each sensor in said pair of sensors in said pluralityof pairs of sensors is capable of conforming to the shape of the portionof skin undergoing measurement.
 11. The apparatus of claim 10, whereineach sensor in said pair of sensors in said plurality of pairs ofsensors is spring-mounted to the surface such that a constant bearingpressure of the portion of skin on each of said sensors is produced. 12.The apparatus of claim 10, wherein each sensor in said pair of sensorsin said plurality of pairs of sensors is pivotably mounted to thesurface.
 13. Apparatus for measuring at least one chosen property of aportion of skin, and for detecting imprecise placement of the portion ofskin onto sensors adapted for such measurements and disposed on asurface of said apparatus, said apparatus comprising in combination: atleast one main sensor disposed on the surface and defining an areathereon, said at least one main sensor having an electrical outputresponsive to a first skin property being measured; at least oneauxiliary sensor disposed on the surface and outside of the area definedby said at least one main sensor, said at least one auxiliary sensorhaving an electrical output responsive to a second skin property beingmeasured; and a processor for receiving and for analyzing the electricaloutput from said at least one main sensor and from said at least oneauxiliary sensor when the portion of skin is placed in contact with saidapparatus; whereby the electrical output from said at least one mainsensor is analyzed and used in the measurement of said chosen propertyonly if said at least one auxiliary sensor has an electrical output. 14.The apparatus of claim 13, wherein the first skin property and thesecond skin property are the same.
 15. The apparatus of claim 13,wherein the at least one chosen property is selected from the groupconsisting of skin temperature, circulation, oxygen saturation, surfacehardness, and heat dissipation.
 16. The apparatus of claim 13, whereineach of said at least one main sensor, and each of said at least oneauxiliary sensor are capable of conforming to the shape of the portionof skin undergoing measurement.
 17. The apparatus of claim 16, whereineach of said at least one main sensor and each of said at least oneauxiliary sensor are spring-mounted to the surface such that a constantbearing pressure of the portion of skin is produced on each of said atleast one main sensor and on each of said at least one auxiliary sensor.18. The apparatus of claim 16, wherein each of said at least two mainsensors are spring-mounted to the surface such that a constant bearingpressure of the portion of skin is produced on each of said at least twomain sensors.
 19. The apparatus of claim 16, wherein said at least onemain sensor and said at least one auxiliary sensor are pivotably mountedto the surface.
 20. Apparatus for measuring a chosen property of aportion of skin, and for detecting imprecise placement of the portion ofskin onto sensors adapted for such measurements and disposed on asurface of said apparatus, said apparatus comprising in combination: aplurality of sensors disposed on the surface, each sensor in saidplurality of sensors having an electrical output responsive to the skinproperty being measured; and a processor for receiving and for analyzingthe electrical output from each sensor in said plurality of sensors,when the portion of skin is placed in contact with said apparatus;whereby measurements of the electrical output from said sensors whichare in partial contact with the portion of skin are used to generate acontact area, and the measurement of the electrical output by saidsensors within the contact area are used in the measurement of thechosen property of the portion of skin.
 21. The apparatus of claim 20,wherein the chosen property is selected from the group consisting ofskin temperature, circulation, oxygen saturation, surface hardness, andheat dissipation.
 22. The apparatus of claim 20, wherein each of saidsensors in said plurality of sensors is capable of conforming to theshape of the portion of skin undergoing measurement.
 23. The apparatusof claim 22, wherein each of said sensors in said plurality of sensorsis spring-mounted to the surface such that a constant bearing pressureof the portion of skin is produced on each of said sensors in saidplurality of sensors.
 24. The apparatus of claim 22, wherein each ofsaid sensors in said plurality of sensors is pivotably mounted to thesurface.
 25. Apparatus for measuring the electrical resistance of aportion of skin, and for detecting imprecise placement of the portion ofskin onto sensors adapted for such measurements and disposed on asurface of said apparatus, said apparatus comprising in combination: atleast one main sensor disposed on the surface and defining an areathereon; at least one auxiliary sensor disposed on the surface andoutside of the area defined by said at least one main sensor; at leastone reference sensor, wherein said at least one main sensor and said atleast one auxiliary sensor are capable of measuring electricalresistance in cooperation with said at least one reference sensor. aprocessor for receiving and for analyzing measured electrical resistancefrom said at least one main sensor and from said at least one auxiliarysensor in cooperation with said at least one reference sensor when theportion of skin is placed in contact with said apparatus; whereby ameasured electrical resistance from said at least one main sensor isused in the measurement of the resistance of the portion of skin only ifsaid at least one auxiliary sensor has a measured resistance.
 26. Theapparatus of claim 25, wherein the measured resistance of said at leastone main sensor is obtained using a direct current, and the measuredresistance of said at least one auxiliary sensor is obtained using analternating current.
 27. The apparatus of claim 25, wherein saidprocessor differentiates between the measured resistance of said atleast one main sensor and the measured resistance said at least oneauxiliary sensor.
 28. The apparatus of claim 27, wherein said processorprovides a warning if said at least one auxiliary sensor does not have ameasured resistance.
 29. The apparatus of claim 25, wherein said atleast one main sensor, said at least one auxiliary sensor, and said atleast one reference sensor are capable of conforming to the shape of theportion of skin undergoing measurement.
 30. The apparatus of claim 29,wherein said at least one main sensor, said at least one auxiliarysensor, and said at least one reference sensor are spring-mounted to thesurface such that a constant bearing pressure of the portion of skin isproduced on said at least one main sensor, on said at least oneauxiliary sensor, and on said at least one reference sensor.
 31. Theapparatus of claim 29, wherein said at least one main sensor and said atleast one reference sensor are spring-mounted to the surface such that aconstant bearing pressure of the portion of skin is produced on said atleast one main sensor and on said at least one reference sensor.
 32. Theapparatus of claim 29, wherein said at least one main sensor, said atleast one auxiliary sensor, and said at least one reference sensor arepivotably mounted to the surface.